Paper for producing photographic prints in colors.



Batented Apr 23, 1918.

APPLICATION FILED MAY 24. I915- MfM. yw

To all whom it may concern:

PAENT OFFICE.

HUHN EDWW THORNTON, 0P WEST HAMPSTEAD, LUNIIDON, ENGLAND, ASSIGNOR TU! JUJEEN OWDEN OPRIEN, or MANGHES'IEE, ENGLAND.

PAPER PQP, PRUDUGING PHOTOGNNPHIU PRINTS nu GOLOPIS.

specification of Letters Patent.

Patented Apr. Q3, fdffi.

hppltoatlon filed May M, 1915. Serial No. 30,171.

Be it known that T, JonN EDWARD THORN- roN, a British sub ect, residing at West Hampstead, London, England,have invented certain new and useful Improvements in Paper for Producing Photo raphic Prints in olors, of which the following is a specification.

This invention relates to color photography and its object is to provide means whereby prints may be made in natural colors on paper (or other desired surface) for viewing by reflected light, and printed direct from any type of natural color negative, such as the well-known Lumiere autochrome or other form of screen-type transparency.

Many attempts have been made to produce a satisfactory and simple means of obtaining color prints on paper from color screen negatives. For instance the well -lmown process of Dr. Smith uses a paper coated with dyed elatins that are printed by the light bleaching out portions of the dyed film according to thefiltering efi'ect of the col-- ored negative. Another method, known as the superimposed, uses three prints, one

above the other, either by triple sensitizing and triple printing, or by cementing three differently colored section prints in contact with each other. paper having a highly reflective surface, such as a metal coated surface, then a sensitive gelatino-silver layer exposed and developed thereon printed from a selective color-screen negative, and finally covered by a color screen cemented thereto through which the print is seen. All these methods are useful and interesting, but they do not quite satisfy the requirements of present day photographers, and the present invention seeks to provide a process that will.

The invention will be described in connection with the accompanying drawing, wherem-'- p v Figure 1 represents a sheet of photographic paper prepared in accordance with the present invention and having colored dots.

Fig. 2 represents a prepared sheet'of pa The present invention consists essentially in preparing the paper or other material 1 Another method uses a to be printed upon with a rinting surface of extremely fine sub-divisions or dots of sensitized colored gelatin or other suitable colloid in any desired number of colorssay two, three, four or even morethe dots being round, squareilhexagonal, or other regu-.

lar or irregular s apes, as indicated at 2 in Fig. 1 or formed b crossed lines or of a mpsalc pattern or t e like, as indicated in 153%. 2,3 and 4.

he colored dots upon the surface of the material are so disposed or intermixed that no two juxtaposed dots are of the same color, where an even mixture is desired. But where a preponderance of one or more colors is desired it may be attained by two dots of one color placed next to one dot of another color.

Any suitable dye may be used for coloring the sensitized emulsion, there-being a llmlted number only of dyes available having the necessary properties. They must be capable of being incorporated with the particular form of colloid adopted. They must not re-act upon the sensitizer used.

The sensitizer may be a bichromate salt, such as ammonium, potassium, or sodium bichromate; or it may be a silver salt, such or dyes of a type that will not render the gelatin insoluble, yet capable of being mordanted by the bichromate or else being selfmordanting and requiring no addition. The mordant is necessary in order to revent the dye washing out from its suspen ing colloid during the various operations.

The bichromate sensitizer may be mixed with the dye' and colloid before coating, in which case-the paper must be used soon after manufacture. But for a commercial product intended to be kept an indefinite time before use, the bichromate sensitizer is emitted .at time of manufacture, and the photographer sensitizes the colored sheet 1mmediately before use in the same way that ordinary carbon tissue is sensitized, by immersion in a bath of bichromate, followed by drying, then printing. it

To produce prints, the prepared paper is placed in a printing frame face to face in contact with a colored negative of the the filtering screen-plate type, exposed to daylight, electric are light, or'mercury vapor lamps for the requisite time then developed 1n hot water if the colloid be gelatin, or in cold Water if it be fish glue, albumen, or gum. Developinent is made from the back, after transfer to a support as in the carbon process.

The finished result is a picture in colored dots, the shadows of the negative being represented by a reater or lesser number of insoluble colore dots, the half-tones by insoluble dots of lesser height, and therefore less intensity, while the high lights are represented by clear paper owing to the dots thereon' remaining soluble and washing ofl during development. The colors of the dots rendered insoluble by light are defined by action of the colored dots of the negative.

Where a quicker printin process 1s required silver is used instea of bichromate as the sensitizer. emulsion of the usual type is used,-that is to say one comprising gelatin and silver bromid, or silver chlorid, or a mixture of both. With such emulsion the dyes are incorporated as before, and the mixture applied to paper in fine sub-division in dots or other design in the manner already described.

- After exposure under a colored negative the image is developed by metol, hydroqulnone, glycin, or other non-staining developer; then fixed in sodium thiosulfate; then soaked in a bath of bichromate and alum or other suitable oxidizing solution that is capable of rendering the gelatin insoluble in direct proportion to the amount of metallic silver left in the image, and at the same time bleaching the silver; and finally developed from the back with hot water to' dissolve away the unhardened parts of the gelatin, thus. leaving an image in dots of colored gelatin as in the method already described. But when using this silver method the hot water development may be omitted if desired, because the superfluous gelatin has already been rendered transparent by the bleaching action of the bichromate oxidizing bath upon the reduced silver.

The dots of dyed gelatin or other colloid are applied to the paper by a machine capable of printin or otherwise depositing the colored gelatin ots in such a way that the difl'erent colors are correctly interspaced and are 'not deposited on top of each other.

Instead of colored dots, as shown in Fig. 1, alternating colored lines 3 may be used, as shown in Fig. 2. If it is desired to avoid the necessity for accurate register the colored colloid is applied to the paper in the form of lines that are crossed to produce .either square or diamond shaped dots, as

indicated at 4 and 5, respectively, and 4.

Where two or more colors overlap one an- Figs. 3

. printing from negatives in colors,

In this case a sensitized prepared with a printing other in either method such will have the eifect of introducing black or rather a dark color approachin black which will have the advantage of elping better to define the image.

Another method of applying the colored colloid when three colors are required is to first coat the paper all over with plain gelatin, then print the first two colors in lines or dots of red and green, in self-mordantin dyes, such as chrome-dyes, and then to fil in the spaces between by blue dye that will soak into the plain gelatin but not into the printed and mordanted arts.

A suitable degree of eness of all these dots or lines is about 200 to the inch or 40,000 to the square inch.

A paper such as described is suitable for producing positives, in colors by direct such negatives being made by any known system.

If the negatives be of the type composed of colored dots, it is desirable to insure best results, that the number of dots er square inch should be greater or less on the positive paper than on the negative from which it is printed, to reduce the number of chance superimpositions of same colors.

What I claim as my invention and desire to protect by Letters Patent is 1. A chromatic printing paper for producing positives in colors by direct printing from negatives in colors, such paper being prepared with a printing surface of colloids in a. plurality 0 colors, finely sub-divided and disposed side by side, the colloids thus presenting a plurality of distinct colors, closely adjacent to one another and in very close formation.

2. A chromatic printing paper for producing positives in colors by direct printing from negatives in colors, such paper being prepared with a printing surface of sensitlzed colloids in a plurality of colors finely sub-divided and disposed side by side, the colloids thus presenting a plurality of distinct colors, closely ad acent to one another and in very close formation.

3. A chromatic printing paper for producing positives in colors by direct printing from negatives in colors, such paper being surface of sensitized colloids in a plurahty of colors, finely sub-divided into dots disposed side by side the colloids thus presenting a plurality of distinct colors, closely adjacent to one another and in very close formation.

4. A'chromatic printing paper for producing positives in colors by direct printing from negatives in colors, such paper being prepared with a printing surface comraeaeea ducing positives in colors by direct printing a from negatives injc'olors, such paper being repared with a printing surface of colloids 1n a plurality of colors, the colloid of each color bein finely sub-divided and disposed side by si e, closely adjacent to one another,

colloids of each color being finely sub-di "ided and disposed side by side, closely advjacent to one another, and the colloid of one color overlapping the colloid of another color.

7. A chromatic printing paper for pro-' ducing positives in,ool0rs by direct print-- ing from negatives in colors, such pa er being prepared with a printin su ace of collolds in a plurality of co ors, the colloid of each color being finely sub-divided and disposed side by side, and the colloids of difl'erent colors crossing one another.

8. A chromatic printing paper for producing positives in colors by direct printing from no atives in colors, such paper being prepare with a printin surface of sensitized colloids in a plum ity of colors the colloid of each color being finely sub-divided and disposed side by side, and the colloids of difi'erent colors crossing one another.

9. A ohromaticprinting paper, capable of producing from a colored negative a positive in. colors, such paper having a surface comprising afinely sub-divided colloid in different colors, disposed in juxtaposition to one another, to present to the eye of an observer, a positive picture with full tones,

half tones, and high lights which appear to present unbroken contmuous tones of various colors, but which in reality consist of a conglomeration of detached or broken points or lines arranged in very close formation, and arranged according to the pattern of the color negative.

In testimony whereof I have hereugto set my hand in presence of two subscribing witnesses.

JOHN EDWARD THORNTON. Witnesses: T H. D, Jameson,

0. J. Worm. 

